Craigslist auto-posting over vps (ec2?)

I want to repost an ad every hour on craigslist, on 4 different accounts, so 3 are up at any time (after 15 minute wait). I want to delete the old ad before reposting the new one with each account. I need a program that can do this. I want to do it over a vps or perhaps ec2. I need 4 different IP addresses (can ec2 do that?) I'd write the program myself, but I don't know the best way to do it. What kind of automated scripting works best over a VPS? What's the cheapest place I can run a program every 15 minutes on 4 different IPs, and what kind of scripting should I use?

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